Objectives: In environments with limited economic resources, it is paramount that the cost-effectiveness of competing strategies of management be compared. Our previous work illustrates that the cost-effectiveness of screening to decrease mortality from colorectal cancer (CRC) depends heavily on adherence, and specifically on whether adherence between screening strategies is heterogeneous. The objectives of this study are to: 1. Determine whether there exists heterogeneity in adherence between different CRC screening tests, 2. Utilize prospective rates of adherence to calculate the true incremental cost-effectiveness between competing CRC screening strategies, 3. Identify factors associated with non-adherence to screening. Research Design: Prospective cohort study in which subjects'adherence to CRC screening tests scheduled by their primary care provider (PCP) is measured. Strategies to be evaluated include fecal occult blood testing (FOBT), flexible sigmoidoscopy (FS), colonoscopy, and virtual colonoscopy (VC, when approved for CRC screening). A study survey based on constructs of the Health Belief Model will be administered. Population to be Studied: Patients at average risk for development of CRC. Principal Source of Data: The primary outcome is adherence to CRC screening, defined as completion of the screening strategy scheduled for the subject within 12-months of enrollment, verified through computerized medical records and subject contact. Secondary outcomes include assessment of preventive intention, measured by subject scheduling of CRC tests, calculation of the incremental cost-effectiveness between competing strategies of CRC screening, and identification of survey and demographic items associated with non-adherence to CRC screening. Principal Types of Analysis: Specific objective 1 will compare adherence to FOBT, FS, colonoscopy, and VC. Specific objective 2 will calculate the incremental cost-effectiveness ratio between competing CRC screening strategies incorporating the prospectively derived adherence rates. Specific objective 3 will examine the association between potential predictive factors identified from the study survey and non-adherence to CRC screening. Analytic methods will include Chi-square testing of proportions, linear mixed-effects modeling and logistic regression analysis. PCPs will be examined as random- and fixed-effects in separate models to account for potential clustering of outcomes within PCP practices. Cost-effectiveness analysis will use our published decision analytic models. Public Health: This study will compare adherence to competing screening tests in order to identify the most cost-effectiveness strategy to decrease mortality from CRC. Barriers to screening identified through this study will form the basis of future novel programs to increase CRC screening adherence.